Device and Method for Equalizing Charges of Series-Connected Energy Stores

• US 20080278969A1
• Filed: 03/24/2005
• Published: 11/13/2008
• Est. Priority Date: 06/28/2004
• Status: Active Grant

• Current Assignee: Continental Automotive GmbH (Continental AG)
• Original Assignee: Siemens AG
• Inventors: Bolz, Stephan, Knorr, Rainer, Lugert, Gunter, Gotzenberger, Martin
• Granted Patent: US 7,800,346 B2
• Time in Patent Office: Days
• US Class Current: 363/17
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0018 using separate charge circuits
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A device and method for equalizing the charges of series-connected individual cells of an energy storage device with a DC/DC converter, which draws energy from the energy storage device or from another energy source, charges an intermediate circuit capacitor whose voltage is inverted in a DC/AC converter, converts the alternating voltage via AC bus lines and coupling transformers by way of a rectifier into a pulsating direct current, and charges the cell having the lowest cell voltage with the pulsating direct current.

Claims

1-17. -17. (canceled)

18. A device for equalizing charges of series-connected individual cells of an energy storage device, comprising:

a DC/DC converter connected by way of a switch to a positive terminal of the energy storage device;

a DC/AC converter connected to an output of said DC/DC converter, said DC/AC converter including an intermediate circuit capacitor and a bridge circuit;

two AC bus lines connected to an output of said DC/AC converter; and

a coupling transformer with one or two secondary windings and a rectifier connected between each of said one or two adjacent cells and said AC bus lines.

19. The device according to claim 18, wherein said energy storage device is a double-layer capacitor.

20. The device according to claim 18, wherein said energy storage device comprises a series circuit of accumulators.

21. The device according to claim 18, which comprises a further switch for selectively connecting said DC/DC converter to a further energy source.

22. The device according to claim 18, wherein said DC/DC converter is a current-regulated step-down converter.

23. The device according to claim 18, wherein said bridge circuit of the DC/AC converter is a multiphase circuit, with each phase thereof connected as a half-bridge consisting of two series-connected transistors connected in parallel with said intermediate circuit capacitor.

24. The device according to claim 23, wherein said bridge circuit of said DC/AC converter is self-clocked.

25. The device according to claim 18, wherein a primary winding of each said coupling transformer is connected between said two AC bus lines.

26. The device according to claim 18, wherein each cell of the energy storage device has a coupling transformer with a secondary winding assigned thereto, and wherein said rectifier connected between said secondary winding of said coupling transformer and the cell is configured such that:

a first terminal of said secondary winding of said coupling transformer is connected to a positive terminal of the cell via a diode conducting current to the cell and is connected to a negative terminal of the cell via a diode conducting current away from the cell;

a second terminal of said secondary winding of said coupling transformer is connected to the positive terminal of the cell via a diode conducting current to the cell and is connected to the negative terminal of the cell via a diode conducting current away from the cell.

27. The device according to claim 18, wherein each two adjacent cells of the energy storage device have a coupling transformer with a secondary winding assigned thereto, and wherein said rectifier connected between said secondary winding of said coupling transformer and the cells is configured such that:

a first terminal of said secondary winding of said coupling transformer is connected to a positive terminal of the one cell via a diode conducting current to the cell and is connected to a negative terminal of the other cell via a diode conducting current away from the cell; and

a second terminal of said secondary winding is connected directly to a connection node of the two cells.

28. The device according to claim 18, wherein each two adjacent cells of the energy storage device have a coupling transformer with first and second secondary windings and a center tap assigned thereto, and wherein said rectifier connected between said secondary windings of said coupling transformer and the cells is configured such that:

a first terminal of said first secondary winding of said coupling transformer is connected to a positive terminal of a first cell via a diode conducting current to the cell and is connected to a negative terminal of the second cell via a diode conducting current away from the cell;

a second terminal of said second secondary winding of the assigned coupling transformer is connected to the positive terminal of the first cell via a diode conducting current to the cell and is connected to the negative terminal of the second cell via a diode conducting current away from the cell; and

said center tap of said first and second secondary windings is connected directly to a connection node of the two adjacent cells.

29. A method of equalizing charges of series-connected individual cells of an energy storage device, the method which comprises:

providing the device according to claim 18;

conducting, from the DC/DC converter fed by the energy storage device or a further source of energy, a current to the intermediate circuit capacitor and thereby building up a voltage at the converter for charging the cells;

inverting the voltage with the DC/AC converter and transmitting over the AC bus lines to the secondary side of the coupling transformers;

converting the secondary alternating current by way of the diodes of the rectifier into a rectified, pulsing charge current for the cell with a lowest cell voltage, as soon as the voltage reaches a value corresponding to a sum of the cell voltage of the cell with the lowest cell voltage and one or two diode forward voltages.

30. The method according to claim 29, wherein each cell is assigned a coupling transformer with a secondary winding, wherein a secondary voltage of the coupling transformer in a first phase causes a charge current from the first terminal of the secondary winding through a first diode the cell with the lowest cell voltage, a fourth diode and back to the second terminal of the secondary winding, and in a second phase causes a charge current from the second terminal of the secondary winding through the third diode, the cell, the second diode and back to the first terminal of the secondary winding.

31. The method according to claim 29, wherein a coupling transformer with a secondary winding is assigned to two adjacent cells in each case, wherein the secondary voltage of the coupling transformer in the first phase causes a current to flow from the first terminal of the first secondary winding through the first diode, the first cell with the lowest cell voltage and back to the second terminal of the secondary winding, and the secondary voltage of the coupling transformer in the second phase causes no current to flow.

32. The method according to claim 31, wherein, if the two cell voltages are equal, the secondary voltage of the coupling transformer in the second phase causes a current flow from the second terminal of the secondary winding through the second cell and via the second diode back to the first terminal of the secondary winding.

33. The method according to claim 29, wherein a coupling transformer with two secondary windings and a center tap is assigned to two adjacent cells in each case, and wherein the secondary voltage of the coupling transformer in a first phase causes a current flow from the first terminal of the first secondary winding through the first diode, the first cell with the lowest cell voltage and back to the center tap, and in the second phase causes a current flow from the second terminal of the second secondary winding through the third diode, the first cell and back to the center tap.

34. The method according to claim 33, wherein, if the two cell voltages are equal, the secondary voltage of the coupling transformer in the first phase also causes a current flow from the center tap through the second cell and the second diode back to the second terminal of the second secondary winding, and in the second phase also causes a current flow from the center tap through the second cell and the fourth diode back to the first terminal of the first secondary winding.